© Ana Marçalo




A stranding occurs when a marine animal gets washed ashore and is unable to return to the sea on its own. These comprise a wide variety of taxonomic groups such as cetaceans, sea turtles and birds. Dead stranded animals are considerably more frequent than alive ones. When dead, animals can exhibit different degrees of decay. If alive, they display unusual behaviour on account of stranding induced stress. In Portugal, as in many other countries, there has been an increase on the amount of strandings per year recorded. Such pattern is related with alert promptness and eficiency from all parties envolved, from institutions to citizens, often hinged by local stranding networks available 24/7.

The amount of information that can be gathered from stranded animals consists of a vital contribution to the scientific knowledge regardind such hard-to-monitor oceanic and often threatened species. Furthermore, considering that only a minor portion of dead marine animals actually gets washed ashore and is consequentely spotted by humans, such events provide vital and relevant information in scientific areas such as biology, ecology, veterinary, pollution and fisheries management. The multi-disciplinary commitment that portuguese teams of biologists and veterinarians have dedicated to strandings over the years, yielded the gathering of information on various fields of biology. Of particular importance, is the data relevant to anatomy, phisiology, pathology, pollution, ecology, fisheries interactions and distribution of marine animals, with emphasis on cetaceans, marine turtles and sea birds.

Why they occur?

Strandings, whether deriving from natural or anthropogenic causes, results from the confusion, debilitation and even death of marine animals.These animals can either actively swim or drift until they run aground on the coast. Among the natural causes are infectious and parasitic diseases, lack of food, intoxication (associated with biotoxins produced by algae blooms), weather conditions, oceanographic phenomena and even atypical individual behavior. Exposure to chemical or noise pollution, garbage ingestion (e.g. ingestion of plastic bags by sea turtles) and direct contact with vessels (collision or fishing operations) comprise the most direct anthropogenic causes. Among these, the interaction with fishing gear has been the one that has deserved the most attention and raised growing concern given the environmental and economic repercussions.


© RAAlg team - Common-dolphin entangled on fishing net


© Alfredo Rodrigues - Bottlenose-dolphin with skin lesions, possibly suffering with the Erysipelothrix rhusiopathiae bacteria


© RAAlg team - Internal hemorrhage in a Sei whale


© RAAlg team - Common-dolphin sliced by a motor boat propeller


© RAAlg team - Evidence of a cetacean bite on the dorsal side of a Harbour-porpoise



With your help, every time a stranding notification is registered on this portal, a member of our team will receive a notice by e-mail containing all the information submitted. At that moment, the RAAlg team will try to validate the maximum information based on the photographic record provided by the user, especially regarding the identification of the species, state of decomposition of the animal, location and access.In each case, the RAAlg team will determine the need to visit the site and will prioritize according to other alerts happening simultaneously.

At the same time, the team will try to coordinate with the Maritime Police, SEPNA, ICNF, health companies and landfills, to monitor as closely as possible the removal of carcasses, in order to avoid threats to public health and loss of scientific information. As each alert is considered solved, RAAlg will add specific and validated information regarding the occurrence, to be part of the general statistics available on this page.